1. Chapter 2 The Sea Floor

2. The Water Planet OCEANS Cover 71% of the globe Regulate earth’s climate and atmosphere

3. The Geography of the Ocean Basins Northern Hemisphere: 61% water Southern Hemisphere: 80% water

4. Ocean Basins Four Ocean Basins Pacific: Largest Atlantic Indian Artic: Smallest

5. The Structure of the Earth Earth = 4.5 Formed from the Big Bang:cosmic explosion of dust Occurred 13.7 billion years ago Dust Particles kept colliding until planets formed.

6. Early Earth Early earth was most-likely MOLTEN. As earth cooled: Densest material flowed toward center of earth. Lighter materials floated toward the surface.

7. Earth Began to Cool As Earth Cooled: Atmosphere formed Oceans formed

8. Internal Structure of Earth Core inner-most layer Composed of iron

9. Internal Structure of Earth Mantle Molten-solid rock Flows around core like liquid

10. Internal Structure of Earth Crust Outermost, best- known layer Thin Floats on Mantle

11. Two Types of Plates Make Up the Earth’s Crust ContinentalOceanic CompositionGraniteBasalt DensityLess DenseMore Dense Age (oldest rocks) 3.8 Billion Years Old200 Million Years Old Elevation Above Sea LevelBelow Sea Level

12. The Origin and Structure of Ocean Basins THE EARTH IS IN A STATE OF CONSTANT TRANSFORMATION.

13. Early Evidence of Continental Drift Sir Thomas Bacon (1620): noticed the coasts of continents fit together like puzzle pieces. Alfred Wegener (1912): Proposed continental drift hypothesis. “All Continents were once joined”: PANGAEA

15. Pangea

16. The Theory of Plate Tectonics Wegener’s hypothesis was not widely accepted because he could not explain HOW continental drift occurred.

17. The Theory of Plate Tectonics 1950s-1960s: Scientists had enough evidence to conclude that continents did “drift.” PLATE TECTONICS

18. Discovery of the Mid-Ocean Ridge Sonar lead to discovery during WW2 Continuous chain of volcanic mountains that encircle the globe

20. Significance of the Mid-Ocean Ridge The Sea floor is created at the Mid- Ocean Ridge

21. Magnetism of Ocean Floor Rocks BACKGROUND: Earth magnetic field reverses direction every few million years. Many rocks contain tiny magnetic particles & these move in molten rock. When the rock solidifies the particles freeze in their orientation Geologists found patterns of magnetic bands or stripes in the sea floor running parallel to the mid-ocean ridge The bands are symmetric around the ridge Magnetic bands = magnetic anomalies

23. How is the Sea-floor Created??? 1. Magma pushes through the mid- ocean ridge 2. Magma cools to form new sea floor 3. As more magma pushes through, the sea floor spreads out— SEA-FLOOR SPREADING

25. Sea-Floor Spreading & Plate Tectonics Earth’s surface is broken into plates. Plates are made of crust and top layer of mantle: LITHOSPHERE Plates spread 2-18 cm per year. (Fingernails grow 6 cm per year.)

26. Plate Movement As plates move, they collide with other plates. *USUALLY* Subduction Occurs: one plate is forced into the mantle when 2 plates collide.

28. Types of Collisions Oceanic- Oceanic Trenches (deep cracks in the crust) are formed.

29. Types of Collisions Continental- Oceanic Trenches produced.

30. Types of Collisions Continental- Continental: produces mountains.

31. Sliding Plates Sometimes plates slide past each other Faults are formed from this process Earthquakes are produced from this process

32. What Makes Plates Move??? SLAB PULL: oceanic crust becomes too heavy to float on the mantle and it sinks down into it, pulling the rest of the plate with it (slowly).

33. Geological History of the Earth Continents were once united: PANGAEA PANGAEA: began to break up 180 million years ago.

34. Geological Provinces of the Ocean

36. Types of Continental Margins Active: Narrow shelves Steep Slopes Little or no rise *Example: Pacific Coast of North America

37. Types of Continental Margins Passive Wide shelves Gentle slopes Well-developed rise *Example: Atlantic coast of North America

38. Deep Ocean Basins Deep-sea floor (ABYSSAL PLAIN): average of 4,000 m deep (13,000 ft)

39. Features of the Deep-Sea Floor Trenches :the deepest part of the ocean floor Rift Zone: break in the earth’s crust from which lava flows and new seafloor forms. Seamounts :submarine volcanoes Guyots: flat-topped volcanoes (INACTIVE) Abyssal Plain: flat part of seafloor Abyssal Hills : small hills Plateaus: flat-topped mountains

41. Guyots Flat-topped seamounts

42. Trenches Deepest parts of the ocean. Deepest: 36,163 ft.

43. Mid-Ocean Ridge and Hydrothermal Vents Central Rift Valley Located in center of Mid-Oceanic Ridge where plates are pulling apart.

44. Hydrothermal Vents Deep-sea hot springs Formed when water that has been heated by the mantle forces its way through the earth’s crust

45. Black Smokers Chimney-like structures Build up around vents Release “clouds” of minerals that have been heated by the vents